Process for precipitation of zinc.



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entrain snares Parana @FFIQE FRANK LAKE WILSON AND SIDNEY ELLIOTT BRE'IHEE'ION, OF BERKELEY, CALIFORNIA.

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To all whom it may concern:

Be it known that we, FRANK L. WinsoN and SIDNEY E. BRETHERTON, citizens of the United States, and residents of Berkeley, in the county of Alameda and State of California, have invented a new and Improved Process for Precipitation of Zinc, of which the following is a full, clear, and exact description.

The purpose of this invention is to obtain a constant precipitation of-metallic zinc from an electrolytic bath and obviate the necessity of installing reduction furnaces for the production of the same.

To carry out the above outlined object, we maintain the concentration of zinc ions in the electrolyte constant, and we obtain this by the addition of a zinc-containing substance to the electrolytic bath.

Our process is especially intended for the continuous precipitation of metallic zinc from either a hot or cold bath of electrolyte of zinc sulfate (ZIISOQ or zinc chlorid (ZnCl The solution of zinc sulfate or chlorid of a proper strength is introduced into a vat provided with anodes and cathodes, the solution forming electrical connection between these electrical poles, so that when the electric current is passed the electrolyte, hot or cold, under the action of the electric current decomposes, and the metallic Zinc precipitates at the cathode while the radical ions of the acid are evolved at the anode. Thus the ionic strength of the solution in zinc decreases while the acid in the solution becomes concentrate. To keep the ionic strength of zinc constant and prevent the concentration of the acid in the electrolytic bat-h, we add to this solution intermittently or continuously zinc oxid (ZnO) or zinc carbonate (ZnCO or both together, pure or contaminated, while the bath is under the action of electric current. The addition of these substances to a bath of either zinc chlorid or zinc sulfate may be expressed by the reaction as follows ZnO+2HCl=ZnC1z+H2Q ZnCOg+2HCl==ZnCl +Ct) -I-H O.

zno+msoi=znsoi+nio ZnCO +HzSO4=-ZIISO4+CO2+ 2Q The above equations show the reaction of the hydrochloric acid and the sulfuric acid present in the respective baths due to the precipitation of metallic zinc and which is Specification of Letters Patent.

Patented Jan, 65, 12914.

Application filed January 28, 1913. Serial No. 744,654.

prevented from concentration by the addition of the zinc oxid or zinc carbonate, or both together. The reaction for both together in a bath is not shown, as it can be easily figured out from the two reactions shown for Zinc (mid and zinc carbonate.

We also add to the electrolyte ammonium carbonate (NH,) CO to form in the bath ammonium sulfate (NHQSO, or ammonium chlorid, each of which causes a better and more uniform precipitation of metallic zinc at the cathodes, from an electrolyte of Zinc sulfate or chlorid, respectively; that is, it adds to the transmission of the ions and acts as a catalytic agent. The addition of ammonium carbonate can be made directly, or the zincoxid and zinc carbonate added are contaminated with ammonia (NH and free carbon dioxid (CO When pure zinc oxid or zinc carbonate is used the addition of ammonium carbonate can be made direct to the bath. The reaction is as follows zno+2nri NH4)2co.,+oo2+0no1= ZnClz+4NH4Cl+2UO2+2H Q The above represents the reactions occurring when the zinc carbonate and the zinc oxid are contaminated with ammonia'and carbon dioxid. These gases cling more or less to the precipitate and unless thoroughly dried will remain and pass into the electrolyte.

lVhen the ammonium sulfate or chlorid becomes too concentrated it proves a detriment to the precipitation of the metallic zinc. The fouled solution is then passed to proper stills where the ammonium is recovered, lime being used to free the ammonia. ,7

(NH4) S04+C&O=CaSO4+2NH3+H O.

As the zinc carbonate is generally more or less hydrated, another reaction maytake We find that the coefliciency in the hydrated zinc carbonate is 3; that is, the formulafor hydrated zinc carbonate may be written as ZnCO,.3H,O Other complete reactions, as shown before for zinc oxid and zinc carbonate, can be similarly expressed with the hydrated zinc carbonat It can be easily seen that with our process, by the addition of a zinc ox id and zinc carbonate, the ionic strength of zinc in the electrolytic bath is maintained constant. This permits a constant precipitation of metallic zinc by means of the electric current, and the addition of ammoniacarbonate to the electrolyte makes the precipitation more uniform.

While to all the reactions described ammonium ca'rbonate was used, acid ammonium fcarbonate can as well be used for the same purpose, as it can be easily seen without showing its'reaetions by means of equation,

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. The process for the continuous pre'cipi tationof metallic zinc, which consists in formlng a solution of zinc sulfate, then introducing said solution into a container pros vided with anodes and cathodes, said solution establishing electrical communication between said anodes and cathodes. then passing the current therethrough thereby decomposing said solution', the zinc being deposited on the cathodes, and to said solution adding zinc carbonate to maintain the strength of the solution substantially constant, and similarly adding to this solution ammonium (Bill'bOIliLtC to form an ammonium sulfate which acts as a catalytic agent in the electrolyte, .and the deposit of the zinc on the cathodes is more uniform due to its presence.

2. The process for the continuous precipitation of metallic zinc, which consists in forming a solution of zinc sulfate, then introducing said solution into a container pro VItlOtl with anodes and cathodes, sald solution establishing electrical counmmieation between said anodes and cathodes, thenpassing the current theretltrough thereby docomposing said solution, the zinc being deposited on the cathodes, and to saidsolution adding hydrated zinc carbomite to maintain the strength of the solution substantially constant, and similarly adding acid ammeegzes lution is decomposed, the zinc being deposited on the cathodes, and to the solution adding zinc carbonate to maintain the zinc solution substantially constant, similarly adding to this solution ammonium carbonate to make the precipitation of metallic zinc on the cathodes more uniform, and removing the liberated carbon dioxid and the ammonium by proper means and using the same over again to form the ammonium carbonate. 1

4:. .ln an electro-chemical process for the continuous precipitation of metallic zinc from an electrolytic bath of zinc sulfate, a step consisting in adding zinc carbonate c011- tamihated with ammonia and carbon dioxid to the electrolyte to maintain the ionic strength of the zinc in said bath substantially constant and to make the precipitation of the zinc on the cathodes more uniform by the electric current.

5. In an electro-chemical process for the continuous precipitation of metallic zinc from an electrolytic bath of the same, a step consisting in adding zine carbonate contaminated with ammonia and carbon dioxid to the electrolyte to maintain the ionic strength of the bath substimtially constant and to make the precipitation of the zinc on the cathodes more uniform by the electric current. ".1 1

6. In an eleetro-chemical process for the continuous precipitation of metallic zinc from an electrolytic bath of the same, a step consisting in :ulding zinc carbonate and ammonium carbonate to form in the bath an ammonium salt which acts as a catalytic agent in the electrolyte. 7

In testimony whereof we have signed our names to this specification in the presence of. two subscribing witnesses.

FRANK LAKE WILSON.

- SIDNEY ELLIOTT BRETIIERTON.

Witnesses FLORA HALL,- A. E. Lo'wlun. 

